You successfully correlated rock layers across multiple locations using index fossils.
This is exactly how geologists determine the relative ages of rock layers.
Game
Fossil Hunt
Use index fossils to match rock layers and determine their relative ages.
You are on a fossil hunt. Scientists have uncovered rock layers at three separate locations, and your job is to use fossil evidence to figure out which layers are the same age — and which came first.
Scientists use index fossils to estimate the age of rock layers and reconstruct Earth's history.
Your progress has been restored.
What Are Index Fossils?▼
Fossils are the remains or traces of organisms from the past. Some fossils are especially useful for helping scientists determine the age of rock layers — these are called index fossils.
A fossil makes a good index fossil only if it meets all three of these criteria:
1
Lived for a short period of time — so its fossils only appear in a narrow band of rock layers.
2
Found in many locations — so scientists can use it to compare rock layers across different sites.
3
Easy to recognize — so it can be reliably identified in rock samples from the field.
Why This Matters
Fossils help scientists date rock layers without using a clock. They help compare layers found in completely different parts of the world. And together, they let geologists reconstruct billions of years of Earth history — one layer at a time.
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Horizons Found
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Errors
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Hints Used
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Difficulty
Practice
Field Investigation
Investigate a layer, then search for a matching fossil in a different location to link them.
Includes highlighted index fossils and fewer horizons.Includes more horizons and misleading fossils.
Field Notes
Index fossils appear in exactly one layer per location. Your mission: find matching fossil horizons across all three dig sites, then determine which layers are oldest.
Determine the Age Order
All fossil horizons identified! Click them below in order from OLDEST to YOUNGEST. Use both layer position and fossil age clues.
Game progress is not submittedComplete the puzzle and quiz, then submit to your teacher
Classroom Progress
Classroom Mode
Step 1 — Identify All Fossil Horizons
0 of 3 groups matched
Step 2 — Determine Age Order
Place the fossil horizons in order from oldest to youngest using their position in the rock layers.
Complete Step 1 to unlock age ordering.
Step 3 — Answer the Quiz
🔒 Complete all fossil matches and age ordering to unlock the quiz.
0 / 4 answered
Step 4 — Submit Your Work
Complete all fossil matches, age ordering, and all 4 quiz questions first.
Your work has been submitted! Great fossil detective work.
Learning Science FocusActive Sense-MakingImmediate FeedbackSpatial Pattern RecognitionScaffolded Transfer
MA STE Standards · Grade 6–86.MS-ESS1-4SP6: ExplanationSP4: Data AnalysisCCC1: Patterns